Boot for constant-velocity universal joint and fixing structure for the same

Abstract

A boot for constant-velocity universal joint is retained to a shaft, which has a general surface, a tapered surface, or a vertical surface instead of the tapered surface, and a major-diameter surface that are disposed one after another in this order and coaxially. The boot includes a minor-diameter cylindrical portion, a major-diameter cylindrical portion, a tapered wall portion, or a vertical wall portion instead of the tapered wall portion, and a bellows. The minor-diameter cylindrical portion is retained to the major-diameter surface of the shaft. The major-diameter cylindrical portion is disposed separately away from the minor-diameter cylindrical portion and coaxially therewith. The tapered wall portion is in contact with the tapered surface of the shaft. The vertical wall portion is in contact with the vertical surface of the shaft. The bellows connects the tapered wall portion or the vertical wall portion with the major-diameter cylindrical portion integrally.

1 . A boot for constant-velocity universal joint, the boot being retained to a shaft, the shaft having a general surface, a tapered surface, or a vertical surface instead of the tapered surface, and a major-diameter surface that are disposed one after another in this order and coaxially,
 the general surface exhibiting an outside diameter, and having opposite ends,   the tapered surface exhibiting a minimum outside diameter being defined by the outside diameter of the general surface, and an outside diameter increasing from the minimum outside diameter to a maximum outside diameter gradually in an axial direction away from the general surface,   the vertical surface extending from one of the opposite ends of the general surface in a diametric direction outward and perpendicularly to the general surface, and exhibiting a maximum outside diameter,   the major-diameter surface exhibiting an outside diameter being defined by the maximum outside diameter of the tapered surface or that of the vertical surface,   the boot comprising:   a minor-diameter cylindrical portion having opposite ends and inside and outside diameters, and being retained to the major-diameter surface of the shaft;   a major-diameter cylindrical portion having inside and outside diameters that are larger than the inside and outside diameters of the minor-diameter cylindrical portion, and being disposed separately away from the minor-diameter cylindrical portion and coaxially therewith;   a tapered wall portion, or a vertical wall portion instead of the tapered wall portion,
 the tapered wall portion adjoining one of the opposite ends of the minor-diameter cylindrical portion that faces the major-diameter cylindrical portion, and having inside and outside diameters decreasing from large to small gradually in a direction away from the one of the opposite ends to the major-diameter cylindrical portion, thereby being in contact with the tapered surface of the shaft, 
 the vertical wall portion extending from the one of the opposite ends of the minor-diameter cylindrical portion that faces the major-diameter cylindrical portion in a diametric direction inward and perpendicularly to the minor-diameter cylindrical portion, thereby being in contact with the vertical surface of the shaft; and 
   a bellows connecting the tapered wall portion or the vertical wall portion with the major-diameter cylindrical portion integrally, and having an overall outer configuration being formed as a truncated cone shape substantially.   
     
     
         2 . The boot according to  claim 1 , wherein the tapered wall portion and an imaginary central line of the boot or that of the shaft make an angle “θ” that is 20 degrees or more. 
     
     
         3 . The boot according to  claim 2 , wherein:
 the tapered wall portion and the imaginary central line of the boot or that of the shaft make an angle “θ” that falls in a range of from 20 to 70 degrees;   the tapered wall portion has a length “L”;   the general surface of the shaft has an outside diameter “D”; and   a ratio of the length “L” to the outside diameter “D” falls in a range of from ¼ to ½.   
     
     
         4 . The boot according to  claim 1 , wherein:
 the vertical wall portion has a length “L 1 ”;   the general surface of the shaft has an outside diameter “D”; and   a ratio of the length “L 1 ” to the outside diameter “D” falls in a range of from 1/10 to ¼.   
     
     
         5 . A fixing structure for boot for constant-velocity universal joint, the fixing structure comprising:
 a shaft having a general surface, a tapered surface, or a vertical surface instead of the tapered surface, and a major-diameter surface that are disposed one after another in this order and coaxially,
 the general surface exhibiting an outside diameter, and having opposite ends, 
 the tapered surface exhibiting a minimum outside diameter being defined by the outside diameter of the general surface, and an outside diameter increasing from the minimum outside diameter to a maximum outside diameter gradually in an axial direction away from the general surface, 
 the vertical surface extending from one of the opposite ends of the general surface in a diametric direction outward and perpendicularly to the general surface, and exhibiting a maximum outside diameter, 
 the major-diameter surface exhibiting an outside diameter being defined by the maximum outside diameter of the tapered surface or that of the vertical surface; and 
   the boot according to  claim 1  whose minor-diameter cylindrical portion is retained to the major-diameter surface of the shaft.